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Serial over ST-Link USB on stm32F722

Question asked by David Pekin on Feb 14, 2018
Latest reply on Feb 15, 2018 by David Pekin



I've developed a program reading and writing serial data using USART6 and pins 6 & 7 on GPIOC.  It uses DMA to perform the RX & TX and is working fine.  We thought we might be able to save some wiring effort if we could use the ST-Link serial port on the USB so I changed USART6 to USART3 and the tx rx pins to 8/9 on GPIOD.  I also changed the baud rate way down to 9600 for testing. 


Unfortunately this "simple" change did not work.  When I send a serial command to the ST-Link serial port, the program has a catastrophic failure and ends in an exception.  The transmit and receive callbacks are never fired.


Is there some limitation on the use of the ST-Link serial channel that prevents this?  Also, the failure occurs whether the debugger is running or not.


Thanks for any insight here.